This makes sure generator functions are marked as optimizable for all
configurations where the BytecodeGraphBuilder is used. Note that as
usual AstNumbering is just a heuristic and the underlying compiler can
still bailout from optimization when the compilation pipeline chooses
another compiler that does not support generator functions.

R=bmeurer@chromium.org,hablich@chromium.org

Review-Url: https://codereview.chromium.org/2353793003
Cr-Commit-Position: refs/heads/master@{#39553}